Commercial airplanes and components thereof are increasingly manufactured from composite materials that may require ultrasonic inspection to determine part integrity. In order to perform an ultrasonic inspection, a transducer that transmits and/or receives sound waves must be acoustically coupled to the part. Water or some other liquid is typically disposed between the transducer and the part to be inspected to provide a medium through which sound waves can travel.
Inspection may be performed from one side (i.e., pulse-echo inspections) or from two sides, referred to herein as the through-transmission (TTU) method. The one side, pulse-echo inspection method is not effective on honeycomb core sandwich panels, so the TTU method is needed to inspect such structures. In addition, the TTU method may provide a more detailed assessment of the condition of a part than other methods. For example, TTU inspection can be used to quantify the amount of porosity present in a composite laminate. A TTU inspection is performed by transmitting sound waves into one side of the part and receiving the sound waves on the opposite side of the part using two transducers coupled to the part simultaneously and on opposite sides.
To insure accurate results, the TTU method requires alignment of transducers sending and receiving the ultrasonic waves. Some prior art methods exist for aligning these transducers before the part is placed therebetween. However, for large, complex composite parts, it can be difficult to maintain this alignment.